Add Privacy Policy

#### Footer Link
Currently using [iubenda](http://iubenda.com)'s free version (no custom styling):
![privacy_policy](https://f.cloud.github.com/assets/226228/1749855/216d6308-6548-11e3-8ec9-e5edc9e70f52.png)

#### Popup
![privacy_policy_popup](https://f.cloud.github.com/assets/226228/1749864/141b99c6-6549-11e3-8711-99a712a5199f.png)